Microwave electron tube

ABSTRACT

A microwave electron tube with electrodes - a cathode, an anode and at least one grid. The cathode, the grid and the highfrequency leads coupled to them form the input circuit of the device. The anode, the grid and the high-frequency leads coupled to them form the output circuit of the device. Electric coupling between at least one of the electrodes and its high-frequency lead is accomplished by means of at least one microwave line section. One of the conductors of the microwave line is connected to the electrode and the other conductor, to its high-frequency lead. The two conductors are shorted at the ends opposite to the points at which they are connected to the electrode and to the high-frequency lead and are constructed in the form of surfaces of revolution the size of which is selected so that at the points of connection the impedance is substantially inductive. Such construction of the device makes it highly suitable for use in microwave power amplifiers which operate within a wide frequency band and provides a high efficiency and a high power gain of the device.

United States Patent [191 Ryabinin et al.

[ MICROWAVE ELECTRON TUBE Filed: Aug. 4, 1972 Appl. No.: 278,013

[ Apr. 16, 1974 2,389,271 11/1945 Mouromtseff et al. 315/39 2,870,374l/l959 Papp 315/39 2,945,158 7/1960 Carson.... 315/39 2,909,698 10/1959Gamer.... 315/39 X 3,273,011 9/1966 Brown 315/39 Primary Examiner-JamesW. Lawrence Assistant Examiner-Saxfield Chatmon, Jr. Attorney, Agent, orFirm-Holman & Stern [5 7] ABSTRACT A microwave electron tube withelectrodes a cathode, an anode and at least one grid. The cathode, thegrid and the high-frequency leads coupled to them form the input circuitof the device. The anode, the grid and the high-frequency leads coupledto them form the output circuit of the device. Electric coupling betweenat least one of the electrodes and its high-frequency lead isaccomplished by means of at least one microwave line section. One of theconductors of the microwave line is connected to the electrode and theother conductor, to its high-frequency lead. The two conductors areshorted at the ends op- [52] U.S. Cl 315/39, 315/3951, 331/97,

331/101 poslte to the points at which they are connected to the [51] IntCl U Holj 7 M6 H01 j 19/80 electrode and to the high-frequency lead andare con- [58] Field of searcnh "315/39 39 331/101 structed in the formof surfaces of revolution the size 331/97 of which is selected'so thatat the points of connection the impedance is substantially inductive.Such con- [56] References Cited struction of the device makes it highlysuitable for use in microwave power amplifiers which operate within aUNITED STATES PATENTS wide frequency band and provides a high efficiencyglint}: and a power gain of the device ar et a r 3,492,528 l/1970Doolittle et a1 315/39 10 Claims, 14 Drawing Figures 57 E 55 40 9 H 42 i6/ 49 0 J5 Z5 25 J8 4i 45 45 47 i2 44 6 :1 L 12 fin j 1 I ll 1 ii l I w22 1 Z 57 5 l0 3.7 j, I I 1 i 27 i1? 34 Z 1 J17 J/ f 1 PAIENIEBAPR 15I974 SHEET 1 (IF 9 PATENTEDAPRHS I914 3.805111 SHEET [1F 9iiiiiiiiiiiiiiim WilWlilHliiWiiHiilIiillili fATENTElHPRIS m4 $805111SHEET 5 OF 9 um\mmmmmmmmnmm PATENTEDAPR 16 1974 SHEET 7 0F 9 FIG. 9

PATENTEDAPR 16 I974 v 3 805 111 sum 8 or 9 D E:g:EEEEE :52:

MICROWAVE ELECTRON TUBE BACKGROUND OF THE INVENTION The presentinvention relates to vacuum tubes, more particularly to grid-controlledmicrowave electron tubes. The invention can be utilized in microwavepower amplifiers operating within a wide frequency band.

An electron tube with oscillatory circuits fully built into the envelopeand which displays a low value of equivalent capacitance of theresonators is well-known in the art. This tube, however, can only beused in a frequency range determined by the built-in cavity resonatorsand the possibility of frequency adjustment is limited. This in turnlimits the scope of application of the tube.

There exist microwave electron tubes which contain electrodes a cathode,an anode and at least one grid, and have an input circuit formed by thecathode and the grid and the associated high-frequency leads, and anoutput circuit formed by the anode, grid and the associatedhigh-frequency leads.

When such tubes function as microwave power amplifiers, oscillatorysystems in the form of coaxial or radial line sections are connected totheir high-frequency leads.

A serious disadvantage of such devices is in that large capacitancereflected from the oscillatory systems to the area of the electrodes,the magnitude of this capacitance exceeding by several times themagnitude of the capacitance between these electrodes, especially duringoperation at frequencies which are above the natural resonant frequencyof the device. This markedly re duces the equivalent impedance of theoutput and input resonators when the device operates within a wide bandof amplified frequencies, which fact results in the decreased gain andefficiency of the device.

This disadvantage is caused by the construction of such devices in whichthe electrodes of the input and output circuits are electrically coupledto their highfrequency leads either directly or through a blockingcapacitor.

It is an object of the present invention to provide a new and improvedmicrowave electron tube free of the above disadvantages of well-knowntubes.

A further object of the present invention is to provide a new andimproved microwave electron tube with maximally reduced value ofequivalent capacitance, designed for operation in combination withexternal oscillatory circuits, which ensures a wide range of operatingfrequencies.

Another object of the present invention is to provide a new and improvedmicrowave electron tube wherein the electrical coupling of theelectrodes with the respective high-frequency leads keeps the value ofthe capacitance reflected from the external oscillatory systems to thearea of the electrodes at a minimum or at least not exceeding thecapacitance between these electrodes.

Additionally, it is a further object of the present invention to providea new and improved microwave electron tube which ensures an increase inthe value of the equivalent resistance of the input and outputresonators when operating within a wide range of amplified frequenciesand which displays high gain and efficiency.

The above and other objects of the present invention are attained in amicrowave electron tube wherein at least one of the means for electricalcoupling of one of the electrodes to its respective high-frequency leadis accomplished by the use of a section of a microwave line whose firstconductor is connected to the electrode and the second, to thehigh-frequency lead of this electrode, the two conductors being shortedat an end of the section of the microwave line opposite to the points atwhich these conductors are connected to the electrode and itshigh-frequency lead. The conductors of the microwave line areconstructed in the form of surfaces of revolution the size of which isselected so that the impedance at the points of connection of theconductors to the electrode and its high-frequency lead should beinductive in character.

Such construction of the microwave electron tube described hereinensures a higher power gain and efficiency when signals are amplifiedwithin a wide frequency band and enhances the operational reliability ofthe device as the adjustment for the required operating frequency iscarried out at low-height frequency currents.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be betterunderstood from the following description of its specific embodimentwhen read in connection with the accompanying drawings, in which:

FIG. 1 is an axonometric view of a microwave electron tube, according tothe invention with a microwave line section in the output circuit;

FIG. 2 is a general partly sectional view of the device shown in FIG. 1with a diagrammatic representation of the cathode-grid assembly;

FIG. 3 is a drawing of the device shown in FIG. I with a differentconnection of a microwave line section to the high-frequency anode leada general partly sectional representation view with a diagrammaticrepresentation of the cathode-grid assembly);

FIG. 4 is a diagram showing the connection of electrodes to theirhigh-frequency leads in the device shown in FIGS. 1 and 3;

FIG. 5 is a drawing of still another embodiment of a microwave electrontube, according to the invention, with a microwave line section in theoutput circuit (a general partly sectional view with a diagrammaticrepresentation of the cathode-grid assembly);

FIG. 6 is a diagram showing the connection of electrodes to theirhigh-frequency leads in the microwave electron tube shown in FIG. 5;

FIG. 7 is a diagram showing the connection of electrodes to theirhigh-frequency leads in a microwave electron tube, according to theinvention, with microwave line sections provided in circuit andconnected to the anode and to the screen-grid;

FIG. 8 is a drawing of a microwave electron tube, according to theinvention, with a microwave line section provided in the input circuitand connectedto the oathode a general partly sectional view with adiagrammatic representation of the cathode-grid assembly);

FIG. 9 is a diagram showing the connection of electrodes to theirhigh-frequency leads in the microwave electron tube shown in FIG. 8;

FIG. 10 is a diagram showing the connection of electrodes to theirhigh-frequency leads in the microwave electron tube, according to theinvention, with a microwave line section provided in the input circuitand connected to the control grid;

FIG. 11 is a diagram showing the connection electrodes to theirhigh-frequency leads in a microwave electron tube, according to theinvention, with microwave line sections provided in the input circuitand connected to the cathode and to the control grid;

FIG. 12 a drawing of a microwave electron tube, according to theinvention, which has one microwave line section both in the input and inthe output circuits a general partly sectional view with a diagrammaticrepresentation of the cathode-grid assembly);

FIG. 13 is a diagram showing the connection of electrodes to theirhigh-frequency leads in the microwave electron tube shown in FIG. 12;

FIG. 14 is a diagram showing the connection of electrodes to theirhigh-frequency leads in a microwave electron tube, according to theinvention, which has two microwave line sections both in the input andin the output circuit.

The microwave electron tube will be described below with respect to atetrode version with cylindrical electrodes. However, the invention canbe also used in triode tubes and in microwave electron tubes with flatelectrodes.

The microwave electron tube described herein comprises coaxiallydisposed electrodes a cathode 1 (FIGS. 1-14), a control grid 2, a screengrid 3 and an anode 4.

The cathode 1 (FIGS. 1 and 2) is made up ofa plurality ofdirectly-heated descrete elements uniformly spaced around thecylindrical anode 4 mounted along the longitudinal axis of the device.The cathode elements 5 are equidistant from the surface of the anode 4,so that the cathode 1 and the anode 4 are coaxial with respect to eachother. The upper ends of the cathode elements 5 are attached to an upperflange 6 of the tube casing which also comprises a lower flange 7 and acylindrical side surface 8. The lower ends of the cathode elements 5 areattached by means of a resilient member 9 to a flange 10 which issecured on one side to the upper flange 6 of the casing through a micaspacer lll, a flange 12 and a mica spacer 13 and on the other side tothe lower flange 7 through a mica spacer 14, a flange 15 and a micaspacer 16.

The control grid 2 (FIG. 1) includes rectangular members 17 whichsurround the cathode elements 5 and carry wire turns 18 on the sidefacing the anode 4. The upper ends of the rectangular members 17 areattached to a flange 19 secured by means ofa ceramic insulator 20 to theupper flange 6 of the casing.

The screen grid 3 includes wire turns 21 attached on the edges ofrectangular support members 22 which are, in turn, secured to the flange12 so that the support members 22 form enclosures for the rectangularmembers 17 of the control grid 2. The screen grid 3 has a cup-shapedmember 23 mounted on the support members 24 and a ring 24 mounted on theflange 15.

The screen grid 3 is electrically shorted for high frequency currents tothe cathode 1 by capacitors, one of which is formed by the flanges 6 and12 and the interposed mica spacer 13, and another by the flanges 12 and10 and the mica spacer 11 and still another by the flanges 10 and 15 andthe mica spacer 14.

The cathode 1 (FIGS. 1 and 2) and the control grid 2 are electricallycoupled to their high-frequency leads 25 and 26, respectively, which areactually the butt surface of the flange 6 and the side surface of theflange 19.

The cathode 1, the control grid 2 and their highfrequency leads 25 and26 form the input circuit of the device now being described.

The anode 4 is electrically coupled to its highfrequency lead 27 by asection of a microwave line 28 while the screen grid 3 is electricallycoupled to its high-frequency lead 29 by a capacitor formed by theflange 15, the flange 7 and the mica spacer 16.

The anode 4, the screen grid 3 and their highfrequency leads 27 and 29form the output circuit of the device according to the invention.

The anode 4 is attached to a hollow cylindrical member 30 mounted on adisc 31 which is, in turn attached to a hollow cylindrical member 32secured by means of a ceramic insulator 33 to the lower flange 7 of thecasing of the device according to the invention.

The microwave line 28 is formed by two conductors 34 and 35, one ofwhich, 34, is the outer cylindrical surface of revolution of thecylindrical member 30, connected to the anode 4, and the other, 35, isthe inner cylindrical surface of revolution of a cylindrial member 32and is connected to the high-frequency lead 27 which is the outercylindrical surface of revolution of the same cylindrical member 32. Thesurfaces of revolution which function as the conductors 34 and 35 of theline 28 have circular cross-sections and a constant cross-sectional sizealong the length of the section of the microwave line 28. The basis fortreating the surfaces of revolution as the conductors 34 and 35 of theline 28 lies in the fact that microwave currents propagate only in anextremely thin skin layer (not more than several microns thick) of theconductive material from which the cylindrical members 30 and 32 aremade.

Surfaces of revolution of other types may be likewise used.

The surfaces of revolution which function as the conductors 34 and 35 ofthe microwave line 28 are dis posed coaxially with respect to eachother. At the ends opposite to the points at which the conductors 34 and35 are connected -to the anode 4 and to the highfrequency lead 27 theseconductors are electrically shorted by a conductive surface 36 of thedisc 31.

The size of the cylindrical surfaces of revolution which function as theconductors 34 and 35 is so selected that at the points at which theseconductors are connected to the high-frequency lead 27 the impedance isinductive in character and is commensurate in magnitude with thecapacitive reactance between the electrode to which the conductor 34 ofthe line 28 is connected, in the given embodiment the anode 4, and theelectrode comprised in the same circuit as the electrode to which theconductor 34 is connected, in the given embodiment the screen-grid 3comprised in the output circuit which also includes the anode 4.

Said size of the surfaces of revolution which function as the conductors34 and 35 of the microwave line 28, in the given embodiment the size ofthe cylindrical surfaces is additionally so selected that the electricallength'of the section of the microwave line 28 should be less than whichenables the equivalent capacitance of the section of the microwave line28 to be reduced.

Besides the size of the surfaces of revolution which function as theconductors 34 and 35 of the microwaveline 28, in the given embodimentthe size of the cylindrical surfaces disposed coaxially with respect toeach other is additionally so selected that the wave impedance of themicrowave line 28 at least within the section adjoining the points atwhich the conductors 34 and 35 of the microwave line 28 are connected tothe electrode and to its high-frequency lead, in the given embodiment tothe anode 4 and to the highfrequency lead 27 of the anode 4, is notbelow the capacitive reactance between the electrode to which theconductor 34 of the microwave line 28 is connected, in the givenembodiment the anode 4, and the other electrode comprised in the samecircuit as the electrode to which said conductor 34 is connected, in thegiven embodiment the screen grid 3 comprised in the output circuit whichalso includes the anode 4.

The size of the surfaces of revolution which function as the conductors34 and 35 of the microwave line 28 are so selected as to satisfy theinequality:

Where W the wave impedance of the line 28 over a section adjoining thepoints at which the conductors 34 and 35 of the line 28 are connected tothe electrode and to its high-frequency lead, in the given embodiment tothe anode 4 and to the high-frequency lead 27 (ohms);

X the capacitive reactance between the anode 4 and the screen grid 3(ohms) calculated from the formula;

where fmaximum operating frequency (Hz);

C the capacitance between the anode 4 and the screen grid 3 (F).

The expressions which relate the size of the surfaces of revolutionwhich function as the conductors 34 and 35 of the line 28, to the waveimpedance of the line 28 are well known to those versed in the art. Forthe given embodiment wherein the surfaces of revolution have acylindrical shape and are disposed coaxially with respect to each otherthe ratios between the diameters of the conductors 34 and 35 of themicrowave line 28 are calculated from the formula;

D/d exp (W/60),

where D the diameter of the larger conductor 35 of the line 28;

d the diameter of the smaller conductor 34 of the line 28.

One of the diameters, D or d, is selected so as to suit the structuralarrangement of the device. This problem does not concern the essence ofthe present invention and is quite clear to those versed in the art. Theother diameter is selected so as to comply with the calculated diameterratic D/d.

The length of the section of the microwave line 28 must be such as tocomply with the relation:

where X the impedance of the line 28 at the points of connection to theelectrode and to its high-frequency lead in the given embodiment to theanode 4 and to the high-requency lead 27 (ohms);

X the capacitive reactance between the anode 4 and the screen grid 3(ohms);

k the coefficient which determines commensuration of the X and X.

The coefficient k is preferably selected within the limits of 0.5 to1.5. If the coefficient k is outside these limits the performance of thedevice will deteriorate in proportion to the deviation of thecoefficient k from the limits given above.

The electrical length of the section of the microwave line 28 iscalculated from the formula:

where 0 the electrical length of the section of the microwave line 28equal to the phase shift occurring in the incident voltage wave as itpropagates from the points at which the line 28 is connected to theanode 4 and to its high-frequency lead 27 to the surface 36 of the disc31 which shorts the line 28, and equal to the phase shift occurring inthe voltage wave reflected from the conductive surface 36 as this wavepropagates from the conductive surface 36 to the points at which theline 28 is connected to the anode 4 and to its highfrequency lead 27(el. degrees).

The expressions which relate the geometrical length of the line sectionto its electrical length for an arbitrary shape of the surfaces ofrotation functioning as the conductors 34 and 35 of the line 28 are wellknown (See, for example, the book Theory of Heterogeneous Lines andTheir Application in Radio Engineering by O.N. Litvinenko and V.l.Soshnikov, Moscow, 1964).

Using these expressions the geometrical length of the section of themicrowave line 28 can be calculated from its electrical lengthcalculated as above.

For the given embodiment the geometrical length is found from theformula:

where 1 the geometrical length of the section of the microwave line 28from the points at which it is connected to the anode 4 and to itshigh-frequency lead 27 to the conductive surface 36 of the disc 31 (cm);

A wavelength corresponding to the operating frequency of the device(cm);

0 the electrical length of the section of the microwave line 28 (el.degrees).

For example, if the operating frequency f 1000 MHz ()t 30 cm) and thecapacitance between the anode 4 and the screen grid 3 determined by theconstruction of the device is equal to 5 pF:

The wave impedance W of the line 28 is selected so as to satisfy theinequality:

W? X 31.8 ohms,

Assume that W 50 ohms.

Now the ratio of the diameters of the surfaces of rev olution whichfunction as the conductors 34 and 35 of the line 28 is calculated fromthe formula:

D/d exp (X/) exp (50/60) 2.27

Suppose one of the diameters, say, diameter d, has to be made equal to 3cm to suit the construction of the anode. Then the other diameter, D, iscalculated as follows:

The coefficient k which is selected within the limits of 0.5 to 1.5 ispreferably made close to unity; assuming that k 1. the electrical lengthis calculated from the formula:

=arc tan (kX/W)=a.rc tan (1X31.8/50)=32.5+ n 180 90 where To satisfy theinequality assume that 6 32.5. Now the geometrical length of the sectionof the microwave line 28 can be calculated:

1= 0 x )t/360= 32,5 x 30l360= 2.7 cm 30/4 75 Such arrangement of theoutput circuit in a microwave electron tube, according to the invention,provides high power gain and high efficiency of the device for a wideband of operating frequencies.

Though the conductors 34 and 35 of the line 28 described above were thecylindrical surfaces of revolution, surfaces of revolution of any othershape may be used just as well to obtain the optimum structuralarrangement of the device in various specific cases.

The output circuit of the device, according to the invention, isisolated from its input circuit by means of the cup-shaped member 23(FIGS. 1 and 2), the screen grid 3, the ring 24 and the flange 15.

The device described herein comprises a means for applying supplyvoltages to the electrodes, which includes filament leads 37 and 38, alead 39 supplying voltage to the screen grid 3, a lead 40 supplying biasvoltage to the control grid 2 and a lead 41 supplying DC. voltage to theanode 4. All leads are made in the form of pipe unions. The filamentlead 37 (FIG. 1) is attached by means of a tubular member 42 to theupper flange 6 of the casing. The filament lead 38 is attached to theupper flange 6 of the casing by means of a ceramic insulator 43 securedto a tubular member 44.

The filament lead 38 is connected by two pipes 45 to the flange 10 (thedrawing shows one pipe 45). The lead 39 which supplies voltage to thescreen grid 3 is mounted on the upper flange 6 by means of a ceramicinsulator 46 and a tubular member 47 attached to each other, and isconnected by two pipes 48 to the flange 12 (the drawing shows one pipe48). The lead 40 which supplies bias voltage to the control grid 2 isattached to the flange 19 by means of a tubular member 49. The lead 41which supplies DC. voltage to the anode 4 is attached to a disc 31.

The device, according to-the invention, comprises a means for coolingthe electrodes, including the two pipes 45 of the filament lead 38 whichcommunicate with a channel 50 in the flange 10 so that one of the pipesserves as an inlet, and the other as an outlet for the liquid coolingthe cathode] two pipes 51 of the filament lead 37 which communicate witha channel 52 in the flange 6 so that one of the pipes serves as aninlet, and the other as an outlet for the liquid coolant, two

pipes 48 which communicate with a channel 53 in the flange 12 so thatone of the pipes serves as an inlet, and the other as an outlet for theliquid cooling the screen grid 3, a pipe 54 which serves as an inlet forthe liquid cooling the anode 4, the pipe 54 being secured to the lead 41by means of a washer 55 provided with coolant outlet bores 56 and 57, apipe 58 of the lead 40 which serves as an inlet for the liquid coolingthe grid 2, the coolant being discharged throgh an outlet bore 59 in thelead 40.

The evacuated envelope 60 of the device, according to the invention,comprises a casing made up of the upper flange 6, the lower flange 7,the cylindrical side surface 8, the flange 19, the ceramic insulators20, 33, 43, 46, the cylindrical member 32, the disc 31, the cylindricalmember 30, the anode 4, the leads 37, 38 and 39, the pipes 45, 48 and 51and an exhaust tube 61 used to evacuate the device.

FIG. 3 shows a microwave electron tube similar in construction to thedevice shown in FIGS. 1 and 2.

The different is that in this embodiment the conductor 35 of the line 28is the inner cylindrical surface of revolution of a hollow cylindricalmember 62 connected by an outer conductive cylindrical surface 63 of thecylindrical member 62 with a high-frequency lead 64 of the anode 4,which is actually the side surface of a disc 65. A high-frequency lead66 of the screen grid 3 is the outer surface of a hollow cylindricalmember 67 attached at one end to the flange 7 of the casing and at theother end to the disc 65 by means of a ceramic insulator 68. In thiscase the evacuated envelope 60 comprises the hollow cylindrical member67 (FIG. 3) instead of the hollow member 32 (FIGS. 1 and 2).

FIG. 4 shows the connection of electrodes to their high-frequency leadsin the device described herein (herein-after we will write:diagrammatically shows the microwave electron tube described herein).

A capacitor C,(FIG. 4) is formed by the flanges 7 and 15 (FIGS. 1-3) andan interposed mica spacer and serves to decouple the screen grid 3 (FIG.4) from its high frequency lead 29 (66) for direct current. A capacitorC is formed by the flanges 15 and 17 (FIGS. 1-3) and the interposed micaspacer 14 and by the flanges 10 and 12 and the interposed mica spacer11. A capacitor C (FIG. 4) is formed by the flanges 6 and 12 (FIGS. 1-3)and the interposed mica spacer 13. The capacitors C and C (FIG. 4)short-circuit the screen grid 3 to the cathode 1 for high-frequencycurrents.

The foregoing discussion was confined to electric coupling between oneof the electrodes, viz. the anode 4 and its high-frequency lead 27 (64)accomplished by the use of a section of the microwave line 28. However,in the microwave electron tube described herein any electrode both inthe input and in the output circuits can be coupled to itshigh-frequency lead by means of a section of a microwave line, or acombination of two or more electrodes can be coupled to the associatedhigh-frequency leads by means of two or more sections of a microwaveline.

These embodiments of the invention are discussed in detail below.

FIGS. 5 and 6 show a microwave electron tube, according to theinvention, wherein one of the electrodes contained in its outputcircuit, viz. the screen grid 3, is coupled to its high-frequency lead69 ny means of a section of a microwave line 70 constructed similarly tothe microwave line in the first embodiment of the invention describedabove. Conductors 71 and 72 of the line 70 (FIG. 5) are the cylindricalsurfaces of revolution of hollow cylindrical members 73 and 74,respectively. The conductors 71 and 72 are shorted to each other by aconductive surface 75 of a disc 76.

The conductor 71 of the line 70 is connected to the screen grid 3 bymeans of a capacitor C (FIG. 6) and a cylindrical member 24 (FIG. Theconductor 72 of the line 70 is connected to the high-frequency lead 69of the screen grid 3 by means of a conductive surface 77 of acylindrical member 74. In this case an anode 78 is mounted on a disc 79isolated from the desc 76 by a ceramic insulator 80. A high-frequencylead 81 of the anode 78 is the side surface of the disc 79.

An evacuated envelope 60 of the device comprises the parts 6, 7, 8, 19,20, 33, 37, 39, 43, 45, 46, 51, 61, 78, 80 as well as the discs 76, 79and a cylindrical member 73.

FIG. 7 diagrammatically shows the third embodiment of a microwaveelectron tube described herein, with two sections of the microwave lines28 and 70 in the output circuit.

In this case the coefficient k which determines the commensuration ofthe capacitive reactance X between the electrodes of the output circuitand the impe dance X of the lines 28 and 70 at the points where they areconnected to the electrode and to the highfrequency lead, respectively,is preferably selected within the limits from 0.25 to 0.75.

The embodiments of a microwave electron tube described above make itpossible to obtain higher levels of oscillatory power, higher efficiencyand higher power gain.

In the fourth embodiment of a microwave electron tube described herein,which is shown in FIGS. 8 and 9, the input circuit has a section of amicrowave line 82 constructed similarly to the embodiments describedabove. One conductor 83 (FIG. 8) of the line 82 is connected to thecathode 1 while the other conductor 84 is connected to thehigh-frequency lead 25 of the oathode 1. The conductors 83 and 84 areshorted by a conductive surface 85 of the flange 6. The anode 4 ismounted on the disc 79 which is isolated from the lower flange 7 of thecasing by a ceramic insulator 33.

FIG. diagrammatically shows still another embodiment of a microwaveelectron tube described herein, wherein a section of a microwave line 86in the input circuit electrically couples the control grid 2 with itshigh-frequency lead 26.

FIG. 11 diagrammatically shows an embodiment of a microwave electrontube described herein with two sections of the microwave lines 82 and 86in the input circuit of the device.

The embodiments of a microwave electron tube shown in FIGS. 8-11 makeitpossible to obtain higher power gains.

In the embodiment shown in FIGS. 12 and 13 one section of the microwavelines 28 and 86 is provided both in the input and in the outputcircuits.

Conductors 87 and 88 of the line 86 are constructed in the form ofcylindrical surfaces of revolution shorted by a conductive surface 89 ofa flange 19. The conductor 87 is connected to the control grid 2, theconductor 88, to its high-frequency lead 26.

FIG. 14 diagrammatically shows an embodiment of the invention with twosections of the microwave lines 82 and 86 provided in the input circuitand with two sections of the microwave lines 28 and 70 provided in theoutput circuit.

The embodiments of a microwave electron tube de scribed herein which areshown in FIGS. 12-14 make it possible to obtain a higher level ofoscillatory power, a higher efficiency and a higher power gain.

The embodiments of a microwave electron tube shown in FIGS. 8 and 14 arepreferably used in microwave power amplifiers connected in acommoncathode circuit.

The operating principle of a microwave electron tube described hereinwill be discussed in detail with respect to the first embodiment (FIGS.1-3).

When the device is used in a microwave power amplifier, an inputoscillatory system is connected to its highfrequency leads 25 and 26, anoutput oscillatory system to the high-frequency leads 27 and 29, afilament source to the leads 37 and 38, a power supply of the screengrid 3, to the lead 39, a source of bias voltage for the control grid 2to the lead 40, a DC. supply source of the anode 4 to the lead 41 (theoscillatory systems and the power sources mentioned above are not shownin the drawing).

The input microwave signal excites the input oscillatory system of theamplifier so that voltage is developed across the grid 2 relative to thecathode 1. This voltage influences the electron stream emitted by thecathode l, as a result of which the stream is density-modulated at thefrequency of the oscillations being amplified. The modulated electronstream passes through the control grid 2 and the screen grid 5 and iscollected by the anode 4 and the screen grid 3. This voltage is appliedto the high-frequency leads 27 and 29 and to the output oscillatorysystem-from the side of the anode 4 through the conductors 34 and 35 ofthe line 28 in the form of surfaces of revolution interconnected by theconductive surface 36 and from the side of the screen grid 3 through thering 24 and the capacitor C As the capacitive reactance between theanode 4 and the screen grid 3 is commensurate with the inductiveimpedance of the microwave line 28 at the points it is connected to theanode 4 and to the high-frequency lead 27, the microwave voltage betweenthese electrodes and the microwave voltage at said points of the line 28are close in value, whereas the microwave voltage between thehigh-frequency leads 27 and 29, which is the difference between the twovoltages mentioned above, is low.

From the oscillatory system the microwave voltage is applied to the load(not shown in the drawing) coupled to this system and the load developsuseful microwave power. The load impedance found in the area of theelectrodes, viz., the anode 4 and the screen grid 3, Le, the equivalentload impedance determines the magnitude of the useful microwave power atthe load, the efficiency and the power gain, which are the larger, thehigher is the equivalent load impedance. However, when the microwavepower amplifier operates within a wide frequency band, the equivalentload impedance is inversely proportional to the equivalent capacitanceof the output oscillatory system found in the area of the anode 4 andthes screen grid 3. This equivalent capacitance is made up of thefollowing three components: the capacitance between the anode 4 and thescreen grid 3, the equivalent capacitance of the section of themicrowave line 28 and the capacitance reflected to the area of the anode4 and the screen grid 3 from the output oscillatory system connected tothe high-frequency leads 27 and 29.

A distinctive feature of a mirowave electron tube, according to theinvention, is that the capacitance reflected from the output oscillatorysystem to the area where the electrodes are located is only a fractionof such capacitance in a device wherein the electrode is connected withits high-frequency lead without the use of a microwave line sectionhaving conductors whose length has been selected in accordance with therela tions given above.

Since the capacitance reflected from the oscillatory system to the areawhere the electrodes are located decreases in proportion to the squareof the ratio of the voltage across the high-frequency leads 27 and 29 tothe voltage between the anode 4 and the screen grid 3, which is rathersmall, this capacitance does not exceed a fraction of the capacitancebetween these electrodes. Therefore the equivalent capacitance of theoutput oscillatory system is determined in the main by the capacitancebetween the anode 4 and the screen grid 3 and by the equivalentcapacitance of the section of the microwave line 28, which, provided thelength of the conductors 34 and 35 of the line 28 has been selected inaccordance with the above relations, does not exceed 28.3 percent of thecapacitance between the anode 4 and the screen grid 3.

The marked decrease of the equivalent capacitance of the oscillatorysystem in a microwave electron tube described herein as compared to thedevices wherein the invention has not been provided ensures a higherequivalent load impedance and, consequently, a higher useful power atthe load, a higher efficiency and a higher power gain.

Besides, the efficiency of the oscillatory systems and the reliabilty ofthe device are also improved in view of the fact that the microwavevoltage at the highfrequency leads 27 and 29 and, consequently, at theceramic insulator 33 and high-frequency currents in the oscillatorysystem are low.

A microwave electron tube, according to the invention, whose embodimentsare shown in FIGS. 5-14 operates similarly to the first embodiment whichwas described above. The difference is that in the embodiment of theinvention shown in FIGS. 8-11 the input oscillatory circuit has agreater equivalent impedance found in the area of the cathode 1 and thecontrol grid 2, while in the embodiments shown in FIGS. l214 both theequivalent impedance and the equivalent load impedance are greater.

A microwave electron tube described herein have escential advantagesover a similar device used as a prototype with respect to a number ofperformance characteristics, viz., the efficiency and, especially, thepower gain. The effectiveness of the invention rises with higheroperating frequencies of the device: at a frequency of 500 MHz the powergain increases 21 times.

Besides, the use of the device, according to the invention, in microwavepower amplifiers considerably enhances their reliability.

We claim:

1. A microwave electron tube comprising: electrodes including a cathode,an anode arranged opposite said cathode and at least one grid arrangedbetween said cathode and said anode; high-frequency leads of each ofsaid electrodes; means for electrically coupling each said electrodes toits high-frequency lead, one of said means connecting the anode to itshigh frequency lead being constructed in the form of a section of amicrowave line; a first conductor of said section of the microwave lineconnected at one end of said anode; a second conductor of said sectionof the microwave line connected at one end to the high-frequency lead ofsaid anode, the other ends of said first and second conductors beingelectrically shorted said first and second conductors being constructedin the form of surfaces of revolution whose size is selected so that theimpedance at said points of connection is inductive in character; meansfor feeding supply voltages to said electrodes; an evacuated envelopemeans enclosing said electrodes and said section of the microwave line.

2. A microwave electron tube as claimed in claim 1, wherein saidsurfaces of revolution made up by said first and second conductors arearranged coaxially relative to each other.

3. A microwave electron tube as claimed in claim 1, wherein theelectrical length of said section of the microwave line is less thanwhich ensures the inductive character of the impedance at said points ofconnection.

4. A microwave electron tube as claimed in claim 3, wherein saidsurfaces of revolution have a constant cross-sectional size along thelength of said microwave line section and the length of said microwaveline section is less than a quarter of a wavelength corresponding to theoperating frequency of the tube.

5. A microwave electron tube as claimed in claim 4, wherein saidsurfaces of revolution made up by said first and second conductors arearranged coaxially relative to each other.

6. A microwave electron tube comprising: electrodes including a cathode,an anode arranged opposite said cathode and at least one grid arrangedbetween said cathode and said anode; high-frequency leads of each ofsaid electrodes, said cathode, said grid and the highfrequency leadsthereof defining an input circuit of said tube, said anode said grid,and the high-frequency leads thereof defining an output circuit of saidtube; means electrically connecting each of said electrodes to itshigh-frequency lead thereof, one of said means connecting the anode toits high frequency lead being constructed in the form of a section of amicrowave line; a first conductor of said section of the microwave lineconnected at one end to said anode in said output circuit; a secondconductor of said section of the microwave line connected at one end tothe high-frequency lead of said anode, the other ends of said first andsecond conductors being electrically shorted, said first and secondconductors being constructed in the form of surfaces of revolution whosesize is selected so that at said points of connection the impedance isinductive in character and commensurable in magnitude with a capacitivereactance between said anode connected to said first conductor and theother electrode of said respective one of said input and output circuitsof which said one of said electrodes forms a part and so that the valueof the wave drag of said section of the microwave line, at least acrossthat portion thereof near said points of connection, being no less thansaid value of said capacitive reactance; means for feeding supplyvoltages to said electrodes; an evacuated envelope means enclosing saidelectrodes and said section of the microwave line.

7. A microwave electron tube as claimed in claim 6, wherein saidsurfaces of revolution formed by said first line section said length ofsaid microwave line section being less than a quarter of a wavelengthcorresponding to the operating frequency of said microwave electrontube.

10. A microwave electron tube as claimed in claim 9, wherein saidsurfaces of revolution formed by said first and second conductors arearranged coaxially relative to each other.

1. A microwave electron tube comprising: electrodes including a cathode,an anode arranged opposite said cathode and at least one grid arrangedbetween said cathode and said anode; high-frequency leads of each ofsaid electrodes; means for electrically coupling each said electrodes toits high-frequency lead, one of said means connecting the anode to itshigh frequency lead being constructed in the form of a section of amicrowave line; a first conductor of said section of the microwave lineconnected at one end of said anode; a second conductor of said sectionof the microwave line connected at one end to the high-frequency lead ofsaid anode, the other ends of said first and second conductors beingelectrically shorted said first and second conductors being constructedin the form of surfaces of revolution whose size is selected so that theimpedance at said points of connection is inductive in character; meansfor feeding supply voltages to said electrodes; an evacuated envelopemeans enclosing said electrodes and said section of the microwave line.2. A microwave electron tube as claimed in claim 1, wherein saidsurfaces of revolution made up by said first and second conductors arearranged coaxially relative to each other.
 3. A microwave electron tubeas claimed in claim 1, wherein the electrical length of said section ofthe microwave line is less than 90*, which ensures the inductivecharacter of the impedance at said points of connection.
 4. A microwaveelectron tube as claimed in claim 3, wherein said surfaces of revolutionhave a constant cross-sectional size along the length of said microwaveline section and the length of said microwave line section is less thana quartEr of a wavelength corresponding to the operating frequency ofthe tube.
 5. A microwave electron tube as claimed in claim 4, whereinsaid surfaces of revolution made up by said first and second conductorsare arranged coaxially relative to each other.
 6. A microwave electrontube comprising: electrodes including a cathode, an anode arrangedopposite said cathode and at least one grid arranged between saidcathode and said anode; high-frequency leads of each of said electrodes,said cathode, said grid and the high-frequency leads thereof defining aninput circuit of said tube, said anode said grid, and the high-frequencyleads thereof defining an output circuit of said tube; meanselectrically connecting each of said electrodes to its high-frequencylead thereof, one of said means connecting the anode to its highfrequency lead being constructed in the form of a section of a microwaveline; a first conductor of said section of the microwave line connectedat one end to said anode in said output circuit; a second conductor ofsaid section of the microwave line connected at one end to thehigh-frequency lead of said anode, the other ends of said first andsecond conductors being electrically shorted, said first and secondconductors being constructed in the form of surfaces of revolution whosesize is selected so that at said points of connection the impedance isinductive in character and commensurable in magnitude with a capacitivereactance between said anode connected to said first conductor and theother electrode of said respective one of said input and output circuitsof which said one of said electrodes forms a part and so that the valueof the wave drag of said section of the microwave line, at least acrossthat portion thereof near said points of connection, being no less thansaid value of said capacitive reactance; means for feeding supplyvoltages to said electrodes; an evacuated envelope means enclosing saidelectrodes and said section of the microwave line.
 7. A microwaveelectron tube as claimed in claim 6, wherein said surfaces of revolutionformed by said first and second conductors are arranged coaxiallyrelative to each other.
 8. A microwave electron tube as claimed in claim6, wherein the electrical length of said section of the microwave lineis less than 90*, which ensures the inductive character of impedance atsaid points of connection.
 9. A microwave electron tube as claimed inclaim 8, wherein said surfaces of revolution have a constantcross-sectional size along said length of said microwave line sectionsaid length of said microwave line section being less than a quarter ofa wavelength corresponding to the operating frequency of said microwaveelectron tube.
 10. A microwave electron tube as claimed in claim 9,wherein said surfaces of revolution formed by said first and secondconductors are arranged coaxially relative to each other.